Centerless grinder attachment



Dec. 8, 1959 E. A. THOMPSON 2,915,855

CENTERLESS GRINDER ATTACHMENT Filed Dec. 50, 1957 3 Sheets-Sheet l INVENTOR W [424 14 7/7aMPJo/v BY 3 f/ A ATTORNEY Dec. 8, 1959 E. A. THOMPSON CENTERLESS GRINDER ATTACHMENT 3 Sheets-Sheet 3 Filed Dec. 30, 1957 INVENTOR.

United States Patent Q CENTERLESS GRINDER ATTACHMENT Earl A. Thompson, Ferndale, Mich.

Application December '30, 1957, Serial No. 706,095

'10 Claims. (Cl. 51-103) This invention relates to machine tools and particularly to machine tools for performing centerless grinding operations. Centerless grinders may be operated either as through-feeding machines or as plunge-cut, in-feeding machines. Where the work pieces have their greatest diameters at the surface or surfaces to be finish ground, the through-feed operation is well suited for economical and accurate production. However, with work pieces which are to be ground on more than one diameter, or with work pieces where it is desired to grind the largest diameter concentric to an already established different diameter on the work piece, the economical through-feed method is not possible to use and the parts must be ground by the plunge-cut method which has heretofore been performed only by a slow hand feeding operation or by complex mechanical Work handling devices. With work pieces, moreover, which have their largest diameter upon the surface to be ground, together with a requirement for concentricity with an already established smaller diameter surface on the piece, it has heretofore been impossible to successfully perform centerless grinding operations automatically upon such pieces.

It is an object of the present invention to provide an improved centerless grinding machine which may be operated automatically to feed parts endwise through the machine as received from a supply chute or conveyor.

Another object of the present invention is to provide a centerless grinding machine wherein work pieces having multiple diameters may be centerless ground by a plunge grinding operation, and in which work pieces are fed through the machine and the machine is operated automatically.

A'further object of the present invention is to provide an improved attachment which may be applied to existing centerless grinding machines in order to adapt them readily to perform the types of grinding operations mentioned.

It is another object of the present invention to provide a centerless grinding machine and an attachment having an improved coordinated drive system embodying a mechanico-hydraulic programming unit of improved form.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is illustrated.

In the drawings:

Figure 1 is an end view of a centerless grinding machine incorporating a preferred form of the present invention.

Figure 2 is a fragmentary view on a larger scale of a portion of the mechanism in Figure 1.

Figure 3 is a fragmentary View, partly in section, taken on line 3-3 of Figure 2.

Figure 4 is an enlarged fragmentary view taken on line 44 of Figure 1.

Figure 5 is a fragmentary view taken along the line 5--5 of Figure 3.

2,915,855 Patented Dec. 8, 1959 A Figure 6 is a fragmentary side view of a portion of the i right side of the machine shown in Figure 1.

' Figure 7 is a view, partly in section, along the line 77 of Figure 6.

Figure 8 is a diagrammatic view of a mechanico-hydraulic control system forming part of the machine of Figure 1. v

Figure 9 is a sectional view ofa work piece showing its condition before and after a grinding operation.

In Figure 1 there is shown a centerless grinding machine comprising a base 10 having a grinding wheel head 12 and a regulating wheel head 14 provided, respectively,

With wheel dressing mechanisms 16 and 18. The head 12' is adjustably mounted in a stationary position on base 10 and carries a main spindle, not shown, on which a grinding wheel 20 may be mounted. A suitable axial oscillat:

ing mechanism may be provided. The head 14 is mounted on the base 10 by means of ways to allow inand outfeeding movements and for this purpose is provided with an oscillatable plunge lever 22 operating in the same manner as the usual manual plunge or in-feed lever of a conventional centerless grinder. A manually operated stop screw 24 determines the limits of in-feed motion. The parts thus far described may be of conventional form.

The grinder of Figure 1 includes a work feeding attachment, generally designated 26, which is connected for operation by hydraulic conduits, not shown, with a mechanico-hydraulic programming and driving unit, generally designated 28, driven by an electric motor 246. The program unit 28 also is hydraulically connected to operate a reciprocating hydraulic motor 30 for the infeed lever 22. Motor 30 contains a piston 32, the rod of which is connected to the lever 22 at the pivot 34. Lever 22 is limited in its oscillatory stroke by adjustable stops 36 and 38. The motor 30 is pivotally mounted at 39 on a suitable sub-base plate 40 which is attached to theiregulating wheel head 14. Motor 30 also incorporates suitable hydraulic connection passages 42 and 44.

The base of the machine 10 carries the usual clamp structure 46, within which a work piece rest 48 is ad .justably clamped. The work rest 48 is provided with a work engaging top surface 50 which may be inclined and positioned in accordance with conventional practice. At its inner end, as shown particularly in Figure 5, the rest 48 has a top surface portion 52 positioned at a lower level and joining the surface 50 by means of a step 54.

The regulating head 14 contains the usual regulating wheel 56 but it is dressed so as to have only a limited Work engaging portion, as shown at 58, whilethe reclamp 46. The sub-frame 64 carries an inclined WOIk.

piece supply chute 66 which may be fed from any suitable conveyer device, not illustrated, and down which work pieces 68 may roll by gravity in side-by-side relation. At the bottom of the chute 66,there is provided a cylindrical pusher 70 which may be operated by a hydraulic motor 72 having a piston 74 to the rod of which the pusher 70 is directly connected. The pusher 70, when retracted as shown in Figure 4, allows a work piece to roll down upon the work rest 48 to the position shown at 68 in Figure 2;

When the pusher 70 is projected to the left in Figure 4,

a work piece is pushed endwise into theworking throat formed betweenthegrinding whee1s -20and"56 and'the L- Tr W I. R a. .7

V. 3- other pieces in the chute 66 are held against advance until pusher 70 is again retracted.

With pusher 70 advanced in the position shown in Figure 3, a train of three work pieces 68: is positioned ahead of it with the thirdpiece'ingrindingposition in the working throat and held against advance by;a retractable 'stop 76. The stop 76 is pivotally mounted on a 'sta-j tionary sub-plate 78, as shown in Figure 5, and is operated by a-hydrauliomotor 80. When the piston 82 shiftsv a short distance to the right in Figure 5, the stop 76 will be lifted toallow the pusher 70 to push the train of work pieces "ahead one step. Because of space considerations in some conventional centerless grinding machines, it may be desirable to extend the lower top'face of the work piece rest 48-, as sh'ownin Figure 5 so as to support a finished work piece in'the position 68", until it has progressed farther to the right in Figure-5 where it;may' fall clear of entanglement with portions'of themachine. Where'it is desired to machine work pieces 68 of the'.

' class such as shown in the upper half of Figure 9 which have a maximum diameter zone at 84 (such as formed by welding flash), which it is desired togrind concentrically with previously finished smaller diameter portions at v86,

it is desirable to provide a hold-down roller for the work piece and which is effective upon one or both the diameters 86. Thus, as shown in Figures 2 and 3, thesubframe 64 may be provided with a-journal bearing 88 for a shaft 90. Shaft 90 carries at one end' a roller arm 92 carrying a hold-down rol1er94. At its other end the shaft 90 carries an operating lever 96 which 'is operated by a hydraulic motor 98 having a piston 100.

v For the purpose of motivating the various'movin'g parts which are operated by the hydraulic motors, previously described, the mechanico-hydraulic programming unit 28 is provided. The mechanico-hydraulic drive and. control unit 28 includes a drive motor 246 which, as .show'nin Figure 8, is arranged to drive a self-controlled two spe'e-d transmission, which is shownin the left-hand half of Figure 8. The motor drives the input shaft 248 of the transmission through abelt drive 250; :The inputshaft 248 drives a pinion252 and also the input member of a hydraulically engaged, spring released clutch 254. YPi'nion 252 drives a gear 256 secured to countershaft 258 which carries pinion 260 at its opposite end. Pinion 260 drives a gear 262 and therewith constitutes a set of speed change gears. Gear 262 drives the input member of a second hydraulically engaged, spring released clutchi264. The driven members of clutches 254 and 264 are secured to the opposite ends of a shaft 266 having a'worm 268 thereon and a brakev drum 270. The latter has a spring biased hydraulic motor 272 for engaging the brake. 'Ihe worm 268 drives a Worm wheel 274 secured to thecamshaft275. For the purpose of automatically controlling thestarting, stopping and speed of the transmission, there is provided; a hydraulic control pump 276 driven from fgear 262, which may circulate a body of oil'contained in the transmission housing for control and lubricatingfpuP posesl The pump 276 may deliver to 'a combined accumulator and relief valve comprising a spring loaded piston 278 and also supplies oil to a bankfof controlvalves 280, 282, and 284. In the diagrams, each valve is shown as a two-position valve, spring' biaised to the position illustrated in which the connections shown in 'the' 'crosshatched rectangles are established. Single-headedarr ows are used to indicate flow at rservoirpressure'and double? headed arrows to indicate flow' at pump delivery pressure. Each of the valves, when shifted, establishes the connec tions shown in the 'unhatched rectanglesimmedia'tely b e-' low the hatched rectangles; r

adjustable 'carns 288 and'. 290," resp'ectivelyfwhich are positioned on camshaft'275." 'Inaddition, valve"2 82 has i a hydraplie. holding cylinder 292 which holds'the valve 4 282 in its shifted position until it is released by the shifting of valve 284. Valve 280, in the position shown, delivers pressure fluid to engage the brake 272 and also exhausts fluid from low speed clutch 264. When shifted valve exhausts fluid to release brake 272 and supplies pressure fluid to engage the low speed clutch 264, subject, however, to a conjoint control by the valve 282.

The latter valve, in the position illustrated, exhausts [fluid to release the high speed clutch 254 and places the 10 low speed clutch 264 under the control of valve 280. In

its shifted position, valve 282, provided valve 280 has been shifted, delivers pressure fluid to engage high speed clutch 254 and exhaust-s fluid to release low speed clutch 264. As previously explained, the valve 284 is merely a reset valve for bypassing the holding cylinder 292 to permit valve 282 to return to its spring 'biased position, shown on the drawings. 7

',Thus, energization of solenoid 286 will start the camshaft rotating at slow speed. Thereafter, the cam 288 will shift the transmission to drive the camshaft at'high speed, and still later. the' cam 290 will again shift the transmission to low speed. So long as the solenoid 286 remains energized, camshaft 275 will continue to rotate, .first at a slow speed and then at a-high speed during each revolution, controlling its own speed changes by operation of the cams 28 8 and 290. 7

For the purpose of controlling the drive motor 246 and the solenoid 286, there is provided an electric control circuit connected between a pair of electric supply lines," 30 designated L-1 and L-2. The circuit may include ama'ster relay 294 of the holding type having a manual master start switch 296 and a manual master stop switch 298. Relay 294 controls the motor 246 and also acycle control relay 300 of the holding type having a manual cycle start switch 302 and a manual cycle stop switch 304. The normally open contacts of relay 300, which are of the make-before-break type, control energization of cycle solenoid 286 directly. The normally closed con-; tacts of relay 300 also control solenoid 286 but are in' 40 series with a cam switch 306 mounted on the left end of the master camshaft 275 and arranged to be opened once during each revolution thereof. The arrangement is such that when the cycle stop switch 304 is'operated at any point in the rotation of camshaft 275, relay 300 will be deenergized but solenoid 286 will remain energized until the cam switch 306 opens at the predetermined stopping" point. Operation of the master stop switch 298, how-, ever, will deenergize solenoid 286 immediately regardless of the point in the cycle and will also deenergize motor 246.

to the camshaft 275 and having a contour composedof predetermined riseand fall ramps designed "to produce the motion sequences desired for' one of the'movable:

'Each sectionmay comprise a' parts ofthe machine. single-acting pulsating cylinder'310 having a piston 312 valve, each of which is connected to a reservoir 316 which is preferably pressurized at a'low super-atmosphericpressure. Each, pulsator cylinder 310 communicates by a closed liquid column conduit 318 with one of the hydraulic motors of the machine and thus they together constitute a liquid column type motion transmitting device for transferring the motion of the cam" follower to the fluid motor. Thus, the liquid column 318 of the section a is connected to the head end offluid motor 30 "for operating the in-feed lever 22. Section b; is coli- The camshaft 275 drives a 'number of cam' operated I hydraulic pulsator sections designated a through'd,"in-j clusive. Each section may comprise a'cam 308 secured I the machine element which is connected to the piston of 1 Valve 280 is arranged to beshifted byfsolenoid Valves-282 and .284 are arranged, to be shifted by the;

nected to the fluid motor 98 for operating theiholddown roller; Section c is connected to the fluid motor for operating the retractable stop and section d is connected to the fluid motor 72 for operating the Work piece P sher.

vEach of the fluid motors operates between limit stops which are so arranged that the total displacement of each fluid motor is slightly less than the displacement of the piston 312 in cylinder 310. Thus, at the end of each advancing stroke, a small quantity of fluid is blown over the relief valve to the reservoir 316. During the latter part of, each return stroke, the replenishing valve permits the fluid to be returned as well as any small amount which may have leaked out of the liquid column.

For the purpose of returning each of the fluid motors and their respective transmitter piston 312, the opposite end of each fluid motor is connected with a plenary volume source of fluid under high pressure which is indicated diagrammatically by the circles marked RO. It will be understood that it is preferred to connect the return end of all cylinders together so as to allow for transferring motion from an advancing cam to another cam which is receding whenever possible. It is preferred to utilize a gas loaded liquid accumulator as the plenary volume high pressure source, although it will be understood that other sources such as spring or weight loaded accumulators, variable displacement pumps with pressure compensation, or fixed displacement pumps with relief valve means may be utilized.

In operation with the supply chute 66 filled with a stack of work pieces, as shown in the upper part of Figure 9, and with a train of work pieces in the position shown in Figure 3, a grinding operation is being performed and the in-feed arm 222 will be shifted, first at'a rapid rate and then at a feed rate as determined by the contour of cam 308a and the speed of the camshaft 275. This pushes the regulating wheel 56 toward the grinding Wheel 20. The work piece 28 is supported upon the upper section 50 of work rest 48 by means of its preformed cylindrical surfaces 86 and is held in position by means of the hold-down roller 94. Thus, the Work piece rotates about the center of the cylindrical surfaces which are in contact with the work rest, the hold-down roller, and the regulating wheel. Grinding, however, is performed upon the larger diameter represented by the welding flash which is in contact with the grinding wheel 20 only. During the in-feed movements, the work piece rides up the inclined surface 54} and roller 94 yields upwardly to permit this action, since it is subjected to the constant pressure in the return oil system which acts as a yielding bias.

When the infeeding motion is completed, as determined by the internal feed stop or by the lever 22 contacting stop 36, the two-speed transmission will again shift to rapid speed and cam-308 will retract, allowing return oil pressure to withdraw the regulating wheel. Concurrently, the hold-down roller 94 will be raised by the cam-pulsator section band, simultaneously, stop 76 will be lifted by cam-pulsator section 0 and the pusher 70 will be retracted by cam-pulsator section d. A new work piece will fall in front of the pusher 70 and the latter will again be advanced, pushing the train of work pieces ahead of it and dropping the foremost piece off the end of the work rest 48 to move out of the machine on a suitable exit chute or conveyer, not shown.

During the final motion of the pusher 70, the stop 76 is returned so as to hold a new train of work pieces by the pusher 70 and stop 76, as shown in Figure 3. The roller 94 will also be returned at this time and the infeed level 22 will be started on its rapid advance stroke. Thereupon the transmission will shift to a slow speed drive of the camshaft 275 and the grinding in-feed motion will be completed, as previously described.

It will be seen that the present invention provides an improved centerless grinding apparatus which may take the form of 'a readily applied attachment that may be fitted to existing conventional centerless grinders,

The invention, furthermore, provides a centerlessgrinding machine and attachment which enables work pieces having multiple external diameters to be ground by the centerless method in a fully automatic manner so as to provide concentricity between finished surfaces of different diameters, even though the grinding is performed on a larger diameter than that which locates the work piece. Itwill be understood that grinding may be performed on more than one diameter at the same time byv the use of contour grinding wheels and that the diameter,

or diameters, being ground need not be larger than the,

locating diameter but may be smaller also, depending upon the type of work piece to be ground.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A centerless grinding machine comprising a frame, a grinding wheel journaled on the frame, a regulating wheel journaled on the frame, a work rest positioned to form with the wheels a work piece receiving throat, a Work holding wheel above the rest and opposite the regulating wheel, and means for lifting the Work holding wheel to permit a work piece to pass into the throat longitudinally, the work-engaging surfaces of the grinding wheel and the regulating wheel being staggered axially of the throat whereby work pieces having a stepped cylindrical contour may be positioned by the rest, the regulating wheel, and the holding wheel on one external diameter and be ground by the grinding wheel on a different external diameter.

2. A centerless grinding machine comprising a frame, a grinding wheel journaled on the frame, a regulating 'wheel journaled on the frame, a work rest positioned to form with the wheels a work piece receiving throat, a work holding wheel above the rest and opposite the regulating Wheel, and means for lifting the Work holding wheel to permit a work piece to pass into the throat longitudinally, the work-engaging surfaces of the grinding wheel and the regulating wheel being staggered axially of the throat whereby work pieces having a stepped cylindrical contour may be positioned by the rest, the regulating wheel, and the holding wheel on one external diameter and be ground by the grinding wheel on a different external diameter, said work rest having portions of different height underlying the work throat, only one of which portions is in contact with a work piece.

3. A centerless grinding machine for multi-diameter work pieces comprising a frame having a stationary blade forming a work rest, a rotary means on one side of the work rest including a grinding wheel, said rotary means being provided with a plurality of work piece engaging surfaces in stepped relation whereby to simultaneously engagea work piece along a plurality of cylindrical surfaces of different diameters, a regulating head on the opposite side of the work rest having rotary means provided with a lesser number of Work piece engaging surfaces to engage a work piece along at least one diameter and to remain clear of the work piece along at least one other diameter, infeed mechanism for producing relative motion of the head toward and away from the work rest, work feeding mechanism at one end of the throat for pushing successive work pieces into the throat, a retractable end stop at the opposite end of the throat forming an abutment against which work pieces may be pushed'by the work feeding mechanism, and coordinated driving means for the infeed mechanism, the work feed mechanism, and the end stop whereby a work piece may be located by contact with the blade, the rotary means and the regulating head at spaced points on one diameter and be ground concentrically on another diameter while pa'ssing'through the throat from one end to the other.

4. A centerless grinding machine for multi-diameter forming a work rest, a rotary means on oneside ofthe work rest including a grinding wheel, said rotary means being provided; with a plurality of work piece engaging surfaces in stepped relation whereby to simultaneously engage a workpiece along a plurality of cylindrical surfaces of difierent diameters, a regulating head on the opposite side of the work rest having rotary means provided with a lesser number of work piece engaging surfaces to engage a work piece along at least one diameter and to remain clear of thework piece along at least one other diameter, infeed mechanism for producing relative motion, of the head toward and away from the work rest, work feeding mechanism atone end of the throat for pushing successive work pieces into the throat, a retractable end stop at the opposite end of the throat forming an abutment against which workpieces may be pushed by the. work feeding mechanism, hydraulic motors for operating the infeed mechanism, the work feed mechanism,'and the end stop, and a mechanico-hydraulic programdevice comprising a camshafhmeans for driving the camshaft, and a plurality of liquid column type motion transfer devices operated by the camshaft and connected one to each hydraulic motor. V t

5. A centerless grinding machine for multi-diameter work pieces comprising a frame having a stationary blade: forming a work rest, a rotary means on one side of the work rest including a grinding wheel, said rotary means being provided with a plurality of work piece engaging surfaces in stepped relation whereby to simultaneously engage a work piece along a plurality of cylindrical surfaces of different diameters, one of said surfaces being provided by a hold-down roller shiftabletoward and away from the work, a regulating head on the opposite side of the work rest having rotary means providedwith a lesser number of Work piece engaging surfaces to engage a work piece along at least one diameter and to remain clear of the work piece along at least one other diameter, infeed mechanism for producing relative motion of the head toward and away from the work rest, Work feeding mechanism at one end of the throat for pushing successive work pieces into the throat, and j coordinated driving means for the infeed mechanism, the work feed mechanism, and the hold-down roller whereby a work piece may be located by contact with the blade, the rotary means and the regulating head at spaced points on one diameter and be ground concentrically on another diameter while passing through the throat from one end to the other.

'6. A centerless grinding machine for multi-diameter workpieces comprising a frame having a stationary blade forming a work rest, a rotary means on one side of the work rest including a grinding wheel, said rotary means being provided with a plurality of work piece engaging surfaces in stepped relation whereby to simultaneously engage a work piece along a plurality of cylindrical sur-' faces of different diameters, one ofsaid surfaces being provided by a hold-down roller shiftable toward and away from the work, a regulating head on the opposite side of the work rest having rotary means provided with a lesser number of 'work piece engaging surfaces to engage a work piece along at least one diameter and to remain clear of the workpiece along at least one other i diameter, infeed mechanism for producing relative motion of the head toward and away'from' the work rest, work feeding mechanism atone end of the throat for pushing successive work pieces into the throat, hydraulic motors for operating the infeed mechanism, theworkfeed mechanism, and the hold-down roller, and a mechanico-hydraulic program device comprising a'camshaft, means for driving the camshaft, and a plurality of liquid column type motion transfer devices operated by the camshaft and connected one to eachjhydraulio motor.

automatic feeding -attachment lrbr' a plungecutting centerless'grinder' having a stationary Work rest and a pair of parallel grinding wheels forming a working throat, said attachment comprising an entry chute for feeding workpieces into alignment; with the throat at one end thereof, a pusher shiftable axially of the throat to dispense work pieces one at 'a time from the chute and push them into the throat, a retractable stop at the opposite end of the throat locatedto positionwork pieces end- 10 8. An automatic feeding attachment fora plungecutting centerless grinder having a stationary work rest and a pair of parallel grinding .wheelsforming a working throat, said attachment comprising an entry chute for feeding work piecesvinto alignment with the throat at 'one end thereof, a pusher shiftable axially of thethroat to dispense work pieces one at a time from the chute and push them into the throat, a retractable stop at the opposite end ofthe throat located to position work pieces endwise between the pusher and the stop for grinding, a

wheel feeding device operable to advance and retract one of the wheels transversely of the throat, a mechanicohydraulic programming and driving system including a camshaft, means for driving the camshaft, and a plurality of liquid column type motion transfer devices each operated by. the camshaft and connected respectively to operate the pusher, the stop, and the wheel feed in timed hold-down roller shiftable toward and away from the' work, a wheel feeding device operable to advance and retract one of the Wheels transversely. of the, throat, and a coordinated driving means connected to operate the pusher, the roller, and the wheel feed in a timed program of motions.

lO, An automatic feeding attachment for a plungecutting centerless grinder having a stationary work rest and a pair of parallel grinding wheelsforrning a working throat, said attachment comprising anentry chute for feeding work pieces into alignment with the throat at one end thereof, a pusher shiftable axially of the throatto dispense work pieces one at atime from the chute and push them into the throat, a retractable stopat the oppositeend of the throat located to position work pieces endwise between the pusher and the stop for grinding, a hold-down roller shiftable toward, and away from the work, a wheel. feedingidevice operable to advance and retract one of the wheels, transversely of the throat, a mechanico-hydraulic programming and driving system including a camshaft, Ineansfor driving the camshaft, and a plurality of liquid column type motion transfer deyices each operated by the camshaft and connected respectively to operate the pusher, the roller, and the wheel feed in timed relation.

References Cited in the file of this patent 

